Thousands of bicyclists descended into downtown San Francisco Sept. 28 to commemorate the 20th anniversary of Critical Mass.

The throng of cyclists clogged city streets for several blocks at a time, annoying some drivers as they continued a San Francisco tradition of proclaiming bicycle safety and overwhelming the city with sheer numbers.

“People will swat at flies, but they are more careful around a swarm of bees,” said Ted Thomas, who said he has been riding in Critical Mass events for about 19 years.

People pedaled for close to four hours, covering nearly 20 miles through downtown, the Embarcadero, the Mission and Financial districts. California Highway Patrol Sgt. Steve Ramos said there were up to 5,000 cyclists, but it was hard to tell.

“It’s excessive,” said a delayed man at Fremont and Mission streets who declined to give his name but asked to be identified as a patient, amused and annoyed motorist. “Bike safety is important, but I don’t quite understand this message.”

Longtime Critical Mass rider and bicycle commuter Vance Ingalls said he rides simply because it’s fun.

“The best part is always the tunnel, the Broadway Tunnel,” he said. “It’s just a bunch of screaming, tired bikers.”

Some riders stopped during that high-speed stretch to write Critical Mass birthday wishes in soot on the walls of Broadway Tunnel, and others howled as they raced through the empty thoroughfare.

San Francisco resident Jonathon Conte said he rides Critical Mass every week.

“It’s great because it started here, and now they do it in like 300 cities,” he said, adding that other cities in earlier time zones had wished San Francisco Critical Mass a happy birthday. “There’s no funding. It’s totally grass-roots, and it spread like wildfire.”

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